An Illustrated Introduction to CAN Bus and Automotive Networks
With the increasing complexity of vehicles, it has become necessary to exchange information quickly and efficiently. The Controller Area Network (CAN) bus meets this demand by connecting several control units and transmitting information in a streamlined and efficient manner.
In this illustrated introduction, we will address this subject by presenting different types of automotive networks and explaining what a CAN bus is and how it works. We will showcase the basics of the CAN bus along with images and diagrams that can help learners understand this network.
Table of Contents
What is a CAN bus, and why is it important?
A Controller Area Network (CAN) bus is an application of a network in motor vehicles. This communication network connects different control units, making the exchange of information more efficient.
Instead of having a unique wire for each piece of information, a network allows various information flows to be transported via a single connection.
In a bus network, all control units are connected to each other in parallel, and the information is transferred through the bus. Therefore, all units can send and receive data via the bus.
Automotive networks
Beyond CAN bus, other automotive networks can address vehicle complexity. These options include:
- Local Interconnect Network (LIN);
- Media Oriented System Transport (MOST);
- FlexRay;
- ByteFlight (BMW).
Types of networks
The control units can also be connected to each other in different ways, dividing networks into three types:
- In a star network, the middle control unit often takes the lead.
- In a ring network, all control units pass all information onto each other like a relay.
- In a bus network, each control unit receives the information simultaneously, and no control unit is in charge.
Star network
The star network is based on the Master-Slave principle.
The master is responsible for diverting the data from one control unit to another.
Ring network
In a ring network, the data line runs from one control unit to another.
Information is passed through control units until it is returned to the transmitter. The information flow is always in the same direction.
A master control unit determines which component can transmit a message and when.
Bus network
In contrast to a ring network, all control units in a bus network are connected to each other in parallel.
Therefore, the messages do not pass from one control unit to another but are put on the bus, where all control units receive them at the same time.
An advantage of the bus network is that it is easy to extend.
How does a CAN bus work?
We can compare the CAN bus to the old telegraph line. The post offices (control units) are connected in parallel with the telegraph line (CAN bus), receiving and transmitting messages.
The telegraph operator has the knowledge to transmit a message received from the customer. They choose when to send the information and use the transmit key to put the message onto the telegraph line.
In the CAN bus, the process is similar:
- The microcontroller receives information from the sensors via the application interface.
- It analyses the information, determines what action must take place, and passes the information to the CAN controller.
- The CAN controller knows how the message must be transmitted and chooses a time to do so.
- The CAN interface converts the message into voltages on the CAN bus.
Examples of CAN bus applications
The wash/wipe system
An example of a Controller Area Network (CAN) bus application in cars is the wash/wipe system, which can be seen in this image and in the diagram below.
The door mirror
The difference between a system with a CAN bus becomes clear when we zoom in on a component with several functions.
If we look at the door mirror of a fully equipped vehicle, we come across the following functions:
- Mirror adjustment;
- Mirror heating;
- Camera for 360° view;
- Warning car in blind spot;
- Indicator;
- Outside temperature sensor;
- Folding motor;
- Automatic dimming function;
- Ground lighting.
To send this information in parallel, you would need many wires. Every form of communication and energy runs via two or three wires per function.
If you equip the mirror with a module connected to the network, then, in principle, you only need four wires: one positive, one negative, and two communication wires.
without CAN bus:
1. mirror adjustment
2. mirror heating
3. camera for 360° view
4. warning car in blind spot
5. indicator
6. outside temperature sensor
7. folding motor
8. automatic dimming function
9. ground lighting
1. positive wire
2. CAN bus cables
3. ground wire
These examples give a good overview of how the CAN bus works and showcase this network’s increased efficiency.
Are you looking for a more advanced, hands-on lesson? Try Electude’s T-Varia CAN-bus Lighting Demo, which combines hardware and courseware to teach CAN bus applications.
You can also teach your students the basics of CAN Bus Networks diagnosis using Electude’s Engine Simulator. Watch the video below to learn how:
